[Asterisk-Users] Snom100 GSM

[Steven Critchfield]

On Fri, 2003-05-16 at 10:13, Gary wrote:
> On Fri, 16 May 2003 11:05:47 -0400, Wade Weppler wrote:
> 
> >The latest SNOM 100 firmware seems to help a bit, but GSM is still unusable.
> >This seems to be a SNOM problem, and not an Asterisk problem, as other GSM
> >SIP phones work fine (X-lite).
> 
> Are you sure ??
> 
> with the x-ten lite, gsm seems choppy, yet g711 is clear as a bell.
> 
> i'm wondering that maybe is might be a gsm prob ?

For those that either cross between linux and windows, be aware that the
way GSM is represented is different. A GSM frame is 32.5 bytes. On
Windows they place 2 32.5 byte frames together shifting the second frame
down half a byte to make a 65 byte packet containing 2 frames. On unix
systems, it is standard to just ignore the final 4 bits of the frame,
and therefore we can transmit in 33 byte packets a frame and we don't
use any bit shifting. I'm sure this is where most problems with GSM come
from.
-- 
Steven Critchfield  <critch at basesys.com>